Mass fragmentographic techniques have been used to estimate GABA turnover rates in substantia nigra, N. accumbens, N. caudatus and globus pallidus of rats treated acutely or subacutely with cataleptogenic or non-cataleptogenic antipsychotics. Our results showed that all antipsychotics of either single or repeated injection enhanced GABA turnover rate in N. accumbens. Yet only non-cataleptogenic antipsychotics increased significantly the GABA turnover in substantia nigra and N. caudatus. Thus, our findings suggest that GABAergic neurons in N. accumbens play a functional role in the therapeutic action of antipsychotics and that extrapyramidal symptoms caused by treatment of neuroleptics may be alleviated when the GABAergic activity in the strio-nigral system is enhanced. BIBLIOGRAPHIC REFERENCES: Mao, C.C., Marco, E., Revuelta, A., Bertilsson, L. and Costa, E.: The turnover rate of gamma aminobutyric acid in the nuclei of telencephalon: Implications in the pharmacology of antipsychotics and of a minor tranquilizer. Biol. Psychiatry 12: 329-371, 1977. Mao, C.C., Cheney, D.L., Marco, E., Revuelta, A. and Costa, E.: Turnover times of gamma-aminobutyric acid and acetylcholine in N. caudatus, N. accumbens, globus pallidus and substantia nigra: Effects of repeated administration of haloperiodol. Brain Research, in press, 1977.